Electric-arc furnace



F. VON SCHLEGELL. ELECTRIC ARC FURNACE. APPLICATION FILED JAN. 28. 1920.

Patented Sept. 14, 1920.

PATENT OFFICE.

FREDERICK VON SCHLEGELL, OF EVANSTON, ILLILNOIS.

ELECTRIC-ARC FURNACE.

Specification of Letters Patent.

Patented Sept. 14, 1920.

Application filed January 28, 1920. Serial No. 354,700.

T 0 all 'whomit may concern:

Be it known that I, FREDERICK von SCHLE- GELL, a citizen of the United States, residing at Evanston, in the county of Cook and State of Illinois, have invented'certain new and useful Improvements in Electric-Arc Furnaces, of which the following is a specification. I

My invention relates to improvements in electric arc heating, and more particularly to improvements in the regulation of the are.

The object of the invention is to provide means whereby the arc is drawn automatically by relative movement of the electrodes when current flows therethrough, and whereby the length of the are is automatically regulated in accordance with the current flowing afterthe arc is established.

In the accompanying drawings I have illustrated two embodiments of the invention.

Figure 1 is a sectional elevation of a small electric furnace, the electrodes being shown in vertical elevation;

Fig. 2 is a top plan view of the electrodes and their support; and

Fig. 3 is a diagrammatic view, showing a modified form of the invention.

The electric furnace, which is shown somewhat diagrammatically in Fig. 1, may consist of a suitable refractory body 1 having a removable upper part 2, said furnace be- 7 ing surrounded by a suitable inclosure 3. Above the furnace a frame or support 4 is provided. This support may be adjusted vertically in any suitable manner. For example, a counterbalancing weight 5 may be provided, secured to a cable passing over a pulley 6. The frame carries an insulating plate or support 7, onwhich the electrodes are mounted. The number of electrodes may be varied, depending on the source of current. In Fig. 1 the power supply maybe assumed to be a three-phase line, in which case I provide, preferably, a central stationary electrode 8, surrounded by three electrodes 9 spaced, preferably, equi-distant therefrom and from each other. The electrode 8 is held by a suitable clamp 10 carried by the insulating support 7 Each electrode 9 is carried by a suitable clamp 11,

which, in turn, is supported on a knife edge 12 resting on the support 7 or on a superimposed insulating disk 13. The electrodes 9 are thus mounted in order that they may swing freely about their pivotal supports. The pivotal mounting may be constructed in various other forms. A weight 14 is also provided, the position of which may be adjusted to cause the electrode 9 to swing nor mally to such position that it will contact with the central electrode 8, the contact being made, preferably, at the lower ends of said electrodes. This is the normal position of each electrode 9 when no current is flowing, and is indicated in dotted lines in lonsidering merel the electrode 8 and the right-hand electrode 9 in Fig. 1, it will be seen that these electrodes provide a path for the flow 0f the current when the latter is switched on to the furnace. As soon as the current begins to flow, however, the magnetic fields which surround the two electrodes repel each other, owing to the opposite direction of flow of the current through the two electrodes, thereby causing the electrode 9 to swing away from the electrode 8 and establish an are at the lower end of said electrodes. Whenever the current is interrupted the electrode 9 swings against the electrode 8, thereby establishing contact therewith, whereby the arc is automatically struck by relative movement of the electrodes whenever the circuit is established again.

Heretofore it has been customary in using electric furnacesto establish the are either by a manual adjustment of one or more electrodes, or by means of automatically controlled motors. With the arrangement described herein the arc is established automatically without the complications and eX- pense of auxiliary electrical equipment.

The movement of the electrode, in addition to establishing the arc, serves automatically to regulate the current flowing in the arc, as variations in the length of said are Vary the resistance thereof, causing the current to flow in an inverse proportion. After an adjustment has been made for a desired kilowatt input the conductivity of the arc may be effected by temperature changes, gases in the furnace, or other variable factors, resulting in a variation in the kilowatt input. For example, an increase in temperature increases the conductivity of the arc, tending to permit an increased flow of current, which in turn increases the magnetic repulsion between the electrodes, thereby tending to lengthen the arc, and thus to increase the resistance sufficiently to offset the increased flow of current. The power input is thus maintained substantially constant.

Another advantage of the structure illustrated herein is that with two electrodes substantially parallel the ends thereof burn away at substantially the same rate, so that this shortening of the electrodes does not substantially vary the position of the arc with reference to said electrodes.

The operation of each of the three electrodes'9 is similar to that just described, the three-phase current flowing through each of the. three electrodes, each of said electrodes regulating its own are and reestablish- Fig. 3 illustrates diagrammatically an arrangement for a single-phase circuit, two electrodes being provided, one of which, 15, is secured in the vertically adjustable support 16, and the other of which, 17, is secured in the support 18, which is shown as being supported on knife edges 19, whereby the electrode 17 may swing toward or away from the electrode 15. Such electrodes are connected in circuit with a suitable transformer,

consisting of primary windings 20 and secondary windings 21, or direct current may be used.

The arrangement of electrodes disclosed herein is suitable forthe melting and refining of ferrous and non-ferrous metals, or for any of the many purposes for which electric furnaces are employed. It is not limited to electric furnaces, however, but is adaptable to various uses where a high temperature is desired.

Although the electrodes are shown as being mounted in substantially vertical position, and nearly parallel to each other, it is obvious that they may be arranged in various positions and at other angles as long as they are relatively movable and the adjustment sufiiciently delicate to permit the movement to be controlled by the magnetic fields established.

I claim 1. In an electric arc heater, electrodes, and means supporting one of said electrodes in contact with the other and permitting relative movement of said electrodes under the influence of the magnetic a pair of field set up by the current flowing through said electrodes whereby the electrodes are'in contact when no current. is flowing and whereby an arc is automatically established when current is supplied thereto.

'2. An electric heater comprising a pair of substantially parrallel electrodes, one of said electrodes being pivotally mounted and balanced to contact normally with the other of said electrodes to establish a circuit therebetween, whereby said electrodes may swing apart when current flows to thereby establish an are automatically.

3. In an electric heater, a pair of substantially parallel movable electrodes so positioned and adjusted that each is afl ected by the magnetic field of the other thereby varying the resistance of the are established between said electrodes to regulate the current flowing therethrough automatically.

. 4:. In an electric heater, a fixed electrode, a pivoted electrode supported so that the ends of said electrodes are normally in con-' tact, whereby current flowing through said electrodes will establish opposing fields resulting in a separation of said electrodes thereby striking an arc and thereafter automatically adjusting the length of said arc to regulate the current flowing therethrough. 5. An electric furnace, comprising a chamber having refractory walls with an opening in the top thereof, a pair of electrodes projecting through said opening in substantially vertical position, a pivotal support for one of said electrodes, and means for balancing said electrode to cause its lower end to contact with the lower end of said other electrode.

6. An electric furnace, comprising a chamber having refractory walls with an opening in the top thereof, a pair of electrodes projecting through said opening in substantially vertical position, a .pivotal support for one of said electrodes, means for balancing said electrode to cause its lower end to contact with the lower end of said other electrode, and means for adjusting said electrodes vertically.

7. An electric furnace, comprising a melt-. ing chamber, a plurality of electrodes pro jecting into said chamber from above, one of said electrodes being fixed and the other being pivotally mounted'and normally in contact with said first electrode, and means for varying the relative height of said electrodes and melting chamber. Y

8. An electric furnace, comprising a melting chamber, a supporting member above the same, a vertical electrode secured to said member, a second electrode pivoted to said member, an adjustable weight for adjusting said pivoted electrode to cause it to contact with said first electrode, and means for councarried thereby.

9. In combination,"a pair of substant parallel relatively movable conductors, means for closing a circuit through said ductors, whereby the magnetic fields 5 rounding. said conductors cause said duct-ors to repel each other and. thereby the resistance of the circuit between conductors.

10. The method of regulating an ele ially and consur-

con-

vary said ctric are for heating purposes, which consists in supporting a pair of electrodes in proximity to each other so that said electrodes may vary the distance between themselves under the influence of the magnetic fields set up by the current flowing therethrough.

In testimony whereof I have subscribed my name.

FREDERICK VON SCHLEGELL. 

